(a) Field of the Invention
The invention relates to a light emitting device, and more particularly, to a light emitting device comprising three light emitting diodes (LED) and a phosphor. The phosphor is excited by absorbing lights from first and second light sources to emit a distinct light. The distinct light is blended with a red light from the third light source and unexcited blue lights from the first and second light sources, and a blended light is released to obtain a white light.
(b) Description of the Prior Art
With reference to FIG. 8 showing a curve diagram of natural sunlight (natural white light), a light wavelength of the light therein ranges between 360 and 750 nm.
To manufacture a white light emitting device having a wavelength approaching that of natural sunlight (white light), the Taiwan Patent Publication No. 383508 discloses a light emitting device and a display device, in that a blue light emitting diode serves as a blue light source for exciting a phosphor, such that the excited phosphor emits a light having a wavelength different from that of the blue light. A white light is obtained when the different light is blended with the unexcited blue light emitted by the light source. Referring to FIG. 9, a curve S2 showing a spectrum of the white light obtained is compared with a curve of the natural white light (sunlight) in FIG. 8, and it is observed that a rather large deviation exists between the two curves. A reason behind is that, the “white light” defined by blending the light having a larger wavelength emitted by the phosphor excited by the blue light with the unexcited blue light, when compared with natural sunlight, has unsatisfactory color rendering effects.
Therefore, it is a vital task of the invention as how to provide a white light approaching natural sunlight.